Use correct hash/equality overrides for SkolemTypes

This should be the same as for TypeVar

Author: odersky

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -4626,9 +4626,8 @@ object Types {
     def derivedSkolemType(info: Type)(using Context): SkolemType =
       if (info eq this.info) this else SkolemType(info)
 
-    override def computeHash(bs: Binders): Int = System.identityHashCode(this)
-    override def eql(that: Type): Boolean = this eq that
-
+    override def computeHash(bs: Binders): Int = identityHash(bs)
+    override def equals(that: Any): Boolean = this.eq(that.asInstanceOf[AnyRef])
 
     def withName(name: Name): this.type = { myRepr = name; this }